Aparatus and method for accelerated multi-stage synthesis of quantum dots

Embodiments of the disclosure relate to an apparatus and a method for accelerated multi-stage synthesis of quantum dots (QDs).

Recent years have shown an accelerated development of QDs as energy-efficient luminescent materials. Cadmium-based QDs, such as CdSe, CdTe and CdS, have been promoted from their desired optical properties, etc. However, cadmium-based materials can result in environmental damage and have high toxicity; therefore, the development of high-performing cadmium-free QDs is desired to enable large-scale adoption of QDs by devices.

One example of cadmium-free QDs is indium phosphide (InP). InP is considered the only class of QDs which offers a compatible, or even broader emission color range than the CdSe-based QDs, while eliminating intrinsic toxicity, as InP contains neither Class A elements (Cd, Hg, Pb), nor Class B elements (e.g. As, Se) (Xie et al. J. AM. CHEM. SOC., 2007, 129, 15432; Reiss et al. J. AM. CHEM. SOC., 2008, 130, 11588). However, synthesis of high-quality InP remains challenging. The existing problems include, among others, low photoluminescence quantum yield, poor size distribution, sensitive precursors, and poor control of the stability.

An embodiment provides an apparatus for multi-stage synthesis of QDs that allows precise injections of raw material and temperature gradient and/or step-by-step temperature control during reactions to form and grow the size and/or control the ingredients of QDs with accelerated kinetics.

An embodiment of an apparatus for accelerated multi-stage synthesis of QDs includes an injector which injects a material for producing QDs; a first reactor connected to the injector and including at least one selected from a coil reactor and a plate reactor; a second reactor connected to the first reactor and including at least one selected from the coil reactor and the plate reactor; and a first junction connected between the first reactor and the second reactor and provided with an inlet for injecting the material for producing the QDs.

In an embodiment, each of the first reactor and the second reactor may include a coil reactor, and the first junction may be a cross-junction provided with two inlets for injecting the material for producing the QDs.

In an embodiment, the apparatus may further include a third coil reactor connected to the second reactor and a second junction connected between the second reactor and the third coil reactor.

In an embodiment, the apparatus may further include a fourth coil reactor connected to the third coil reactor; and a third junction connected between the third coil reactor and the fourth coil reactor.

In an embodiment, each of the second junction and the third junction may be the cross-junction provided with the two inlets for injecting the material for producing the QDs.

In an embodiment, each of the second junction and the third junction may be a three-branch junction provided with a single inlet for injecting the material for producing the QDs.

In an embodiment, the first to fourth coil reactors may have independent temperatures and include tubes of which volume (length) are not equal.

In an embodiment, the apparatus may further include a detector positioned next to the second reactor, where the detector measure ultraviolet to visible light to near infrared (UV-Vis-NIR) absorption of the QDs.

In an embodiment, the first reactor may include a first coil reactor, and the second reactor may include a first plate reactor.

In an embodiment, the first junction may be a cross-junction provided with two inlets for injecting the material for producing the QDs or a three-branch junction provided with a single inlet for injecting the material for producing the QDs.

In an embodiment, the second reactor may further include a second coil reactor connected to the first plate reactor, a third coil reactor connected to the second coil reactor, and a fourth coil reactor connected to the third coil reactor.

In an embodiment, the first plate reactor may generate a temperature gradient therein, and the first to fourth coil reactors may have respective independent temperatures.

In an embodiment, the second reactor may further include a second plate reactor connected to the first coil reactor and a second coil reactor connected to the second plate reactor.

In an embodiment, the first plate reactor may include a tube spirally rolled in from an edge to a center of the first plate reactor and spirally rolled out from the center to the edge of the first plate reactor and the second plate reactor may include a tube repeatedly bent to reciprocate in a transverse direction, where the second plate reactor may gradually increase a temperature of the tube from an end connected to the first plate reactor to an end connected to the second coil reactor.

In an embodiment, the second coil reactor may include a tube having a larger inner diameter than a tube of the second plate reactor.

In an embodiment, the apparatus may further include a third coil reactor connected to the second coil reactor; and a second cross-junction connected between the second coil reactor and the third coil reactor.

An embodiment of a method for accelerated multi-stage synthesis of QDs includes injecting a precursor to a first flow reactor, adding the precursor to synthesized quantum dots from the first flow reactor, and transferring a mixture of the synthesized QDs from the first flow reactor and the precursor to a second flow reactor which synthesizes QDs.

In an embodiment, the method may further include adding the precursor to synthesized QDs from the second flow reactor and transferring a mixture of the synthesized QDs from the second flow reactor and the precursor to a third flow reactor which synthesizes QDs.

In an embodiment, the first flow reactor may preheat the precursor injected therein.

In an embodiment, the second flow reactor may include at least one selected from a coil reactor and a plate reactor, where the plate reactor may generate a temperature gradient therein.

The invention now will be described more fully hereinafter with reference to the accompanying drawings, in which various embodiments are shown. This invention may, however, be embodied in many different forms, and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art.

The drawings and description are to be regarded as illustrative in nature and not restrictive. Like reference numerals designate like elements throughout the specification.

In the drawings, the size and thickness of each element may be arbitrarily illustrated for convenience of description, and the disclosure is not necessarily limited to what is illustrated in the drawings. In the drawings, the thickness of layers, films, plate, regions, etc., may be exaggerated for clarity. In the drawings, for better understanding and ease of description, the thicknesses of some layers and regions may be exaggerated.

As used herein, the singular forms, “a,” “an,” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise.

The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting. As used herein, “a”, “an,” “the,” and “at least one” do not denote a limitation of quantity, and are intended to include both the singular and plural, unless the context clearly indicates otherwise. For example, “an element” has the same meaning as “at least one element,” unless the context clearly indicates otherwise. “At least one” is not to be construed as limiting “a” or “an. “Or” means “and/or.” As used herein, the term “and/or” includes any and all combinations of one or more of the associated listed items. For example, “A and/or B” may be understood to mean “A, B, or A and B.” The terms “and” and “or” may be used in the conjunctive or disjunctive sense and may be understood to be equivalent to “and/or.”

In the specification and the claims, the phrase “at least one of” is intended to include the meaning of “at least one selected from” for the purpose of its meaning and interpretation. For example, “at least one of A and B” may be understood to mean “A, B, or A and B.”

It will be understood that, although the terms first, second, etc., may be used herein to describe various elements, these elements should not be limited by these terms. These terms are only used to distinguish one element from another element. For example, a first element may be referred to as a second element, and similarly, a second element may be referred to as a first element without departing from the scope of the disclosure.

It will be understood that when an element such as a layer, film, region, or substrate is referred to as being “on” another element, it can be directly on the other element or intervening elements may also be present. In contrast, when an element is referred to as being “directly on” another element, there are no intervening elements present. Further, throughout the specification, the word “on” a target element will be understood to be positioned above or below the target element, and will not necessarily be understood to be positioned “at an upper side” based on a side opposite to the direction of gravity.

For example, the spatially relative terms “below”, “beneath”, “lower”, “above”, “upper”, or the like, may be used herein for ease of description to describe the relations between one element or component and another element or component as illustrated in the drawings. It will be understood that the spatially relative terms are intended to encompass different orientations of the device in use or operation, in addition to the orientation depicted in the drawings. For example, in the case where a device illustrated in the drawing is turned over, the device positioned “below” or “beneath” another device may be placed “above” another device. Accordingly, the illustrative term “below” may include both the lower and upper positions. The device may also be oriented in other directions and thus the spatially relative terms may be interpreted differently depending on the orientations.

The terms “overlap” or “overlapped” mean that a first object may be above or below or to a side of a second object, and vice versa. Additionally, the term “overlap” may include layer, stack, face or facing, extending over, covering, or partly covering or any other suitable term as would be appreciated and understood by those of ordinary skill in the art.

When an element is described as ‘not overlapping’ or ‘to not overlap’ another element, this may include that the elements are spaced apart from each other, offset from each other, or set aside from each other or any other suitable term as would be appreciated and understood by those of ordinary skill in the art.

The terms “face” and “facing” mean that a first element may directly or indirectly oppose a second element. In a case in which a third element intervenes between the first and second element, the first and second element may be understood as being indirectly opposed to one another, although still facing each other.

In addition, unless explicitly described to the contrary, the word “comprise” and variations such as “comprises” or “comprising”, “include” and variations such as “includes” or “including”, “has” and variations such as “have” or “having” will be understood to imply the inclusion of stated elements but not the exclusion of any other elements.

It will be understood that when an element (or a region, a layer, a portion, or the like) is referred to as “being on”, “connected to” or “coupled to” another element in the specification, it can be directly disposed on, connected or coupled to another element mentioned above, or intervening elements may be disposed therebetween.

It will be understood that the terms “connected to” or “coupled to” may include a physical or electrical connection or coupling.

“About” or “approximately” as used herein is inclusive of the stated value and means within an acceptable range of deviation for the particular value as determined by one of ordinary skill in the art, considering the measurement in question and the error associated with measurement of the particular quantity (i.e., the limitations of the measurement system). For example, “about” can mean within one or more standard deviations, or within ±30%, 20%, 10% or 5% of the stated value.

Unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which the disclosure pertains. It will be further understood that terms, such as those defined in commonly used dictionaries, should be interpreted as having a meaning that is consistent with their meaning in the context of the relevant art and will not be interpreted in an idealized or overly formal sense unless expressly so defined herein.

is a schematic diagram of an embodiment of the apparatus for accelerated multi-stage synthesis of QDs.is a structure diagram of the embodiment of.is a perspective view of a cylindrical body of the coil reactor used in the embodiment of.

Referring to, an embodiment of the apparatus for accelerated multi-stage synthesis of QDs may include a first coil reactor, a second coil reactor, a cross-junctionconnected between the first coil reactorand the second coil reactor, a detectorfor measuring ultra violet to visible light to near infrared (“UV-Vis-NIR”) absorption, and tubes,,, andthrough which materials for synthesis of QDs such as Indium (In) precursor and Phosphorus (P) precursor and synthesized QDs flow. Not illustrated but injectors such as syringe pumps may be connected to the tubes,andfor injecting the materials for synthesis of QDs. The detectoris for measuring the absorption properties of the synthesized QDs, but alternatively may be omitted.

Referring to, the first and second coil reactorsandmay include a cylindrical body provided with spiral thread on a lateral surface thereof and holes for receiving heating sticks. The heating sticksmay heat up the cylindrical body by electrical heating (e.g., Joule heating). The cylindrical body may include or be made of a metal such as stainless steel, aluminum, or copper and have a polygonal cross-section instead of the circular cross-section. The first and second coil reactorsandare examples of flow reactor modules. Alternatively, not illustrated but the first and second coil reactorsandmay be wrapped in aluminum foil to improve heat distribution. In such an embodiment, the first and second coil reactorsandmay be further wrapped in a fiberglass insulating fabric, and finally wrapped in a second layer of aluminum foil to reduce radiative heat loss.

The tubesandare coiled on the cylindrical body along the spiral thread and the tubesandare connected to the branches of the cross-junction. The tubes,,, andmay include or be made of Teflon™ or stainless steel. In an embodiment, Teflon™ perfluoroalkoxy (PFA) may be applied in a reaction performed at a temperature less than or equal to about 250° C. The stainless steel may be applied in a reaction performed at a temperature greater than 250° C. The tubes,,, andmay have an inner diameter in a range from 0.01 inch to 0.1 inch.

The cross-junctionmay have four branches in which passages for material flow are formed to communicate each other. The four branches of the cross-junctionare respectively connected to the tubes,,, and. The cross-junctionmay include or be made of polyetheretherketone (PEEK) or stainless steel.

In an embodiment of the apparatus, the materials for synthesis of QDs (Core 1) such as Indium (In) precursor and Phosphorus (P) precursor or an initial QDs material may be injected together to the tubeand reacted to synthesize QDs on the first coil reactor, then the synthesized QDs are transferred to the second coil reactorthrough the cross-junction. The materials for synthesis of QDs such as Indium (In) precursor and Phosphorus (P) precursor may be additionally injected to the tubesandand transferred to the second coil reactoralong with the synthesized QDs from the first coil reactor. In the second coil reactor, the QDs from the first coil reactorare grown up with the additionally injected materials. The first coil reactormay be used to preheat the materials for synthesis of QDs or the initial QDs material. In such an embodiment of the apparatus, the QDs may be synthesized with a very small amount of the materials for synthesis of QDs or the initial QDs material. The QDs may be synthesized with 0.5 ml to 2 ml of the materials for synthesis of QDs or the initial QDs material, therefore the materials for synthesis of QDs or the initial QDs material may be significantly saved. To reduce the amount of the materials for synthesis of QDs or the initial QDs material, a spacer gas or liquid may be used to fill the space in the tubes,,, and, which is not occupied by the materials for synthesis of QDs or the initial QDs material.

is a schematic diagram showing an embodiment of a method of synthesizing QDs using the apparatus of.

An initial QDs material is injected into the first coil reactorby an injectorsuch as a syringe pump. The injection may be performed at the volumetric flowrate in a range from about 50 uL/min to about 5000 uL/min. The first coil reactormay be set to have a temperature in a range from about 260° C. to about 320° C. The initial QDs material is instantly heated up to the reaction temperature in a range of about 260° C. to about 320° C. while flowing through the tube of the first coil reactor. The heated QDs material flows to the cross-junctionand is mixed with the materials for synthesis of QDs such as Indium (In) precursor and Phosphorus (P) precursor which are additionally injected at the cross-junction. The Indium (In) precursor may be Indium palmitate (In(PA)), which is an example of Indium carboxylate, and may be injected at a speed of about 60 uL/min to about 600 uL/min. The Phosphorus (P) precursor may be a solution of Tris(trimethylsilyl)phosphine and Trioctylphospine (TMSP/TOP) and may be injected at the volumetric flowrate of about 30 uL/min to about 300 uL/min. The mixture of heated QDs material and the materials for synthesis of QDs flows into the second coil reactorand reacts to grow the size of the QDs (Cycle 1). The QDs material output from the second coil reactor(Core 2) in Cycle 1 is injected again into the first coil reactorand the same process as Cycle 1 is repeated twice (Cycles 2 and 3) or more. Through this repetition of the single injection cycle, the initial QDs are grown up to a predetermined size, causing a red shift in the first excitonic peak absorption wavelength. Therefore, a blue QDs may be grown up to a green QDs or a red QDs.

is a schematic diagram showing an embodiment of a method of synthesizing QDs using an alternative embodiment of the apparatus for accelerated multi-stage synthesis of QDs.